1. Technical Field
This invention relates generally to wet shaving devices, and more specifically to razor handles including hand gripping pads.
2. Background Information
Many modern safety razors include a disposable razor cartridge adapted to be selectively connected to a reusable handle by cartridge support structure therebetween. The cartridge includes a housing having at least one razor blade with a sharpened cutting edge disposed therein. The handle can be provided with gripping pads having on their exterior surfaces an elastomeric, ie rubber-like material. A normal wet shaving operation is typically performed in an environment that can cause a razor handle to be wet and/or slippery due to the shaving soaps or other preparations employed by the user. The elastomeric material provides the user with at least a sense of a more secure grip of the handle in these circumstances and can help prevent nicks and cuts that might be caused by the user mishandling the razor or can help prevent the user accidentally dropping the razor.
Exemplary razors with elastomeric gripping pads are disclosed in U.S. Pat. Nos. 5,822,869 and 5,890,296, both to Metcalf et al. These Patents disclose razor handles having elongated hand-gripping structures that include a frame and at least two gripping pads disposed on opposed sides of the frame. Each gripping pad has a non-elastomeric support layer with an elastomeric gripping layer molded thereon. The support layer of each gripping pad is provided with several extensions that are press fitted into mating elongated slots of the frame to provide the joint between the frame and each respective gripping pad. In consideration of the selection of a press fit joint over other suitable joining methods, one of skill in the art will understand that the retention or security of attachment properties of a typical press fit joint are dependent upon several characteristics of the joint including a property of many molded thermoplastics known as creep modulus and the provision a controlled difference in size, or interference, between the extension and one or both sides of its mating slot or opening. Creep modulus can be likened to a time-dependent relaxation effect which can cause the resistance to disengagement of a press fit joint to diminish over an extended time period. A controlled interference can provide a somewhat uniform assembly or insertion force of the press fitting parts and is preferred at least for manufacturing reasons.
So-called commodity thermoplastics of the olefin family such as polypropylene (PP) and derivatives of polyethylene (HDPE, LDPE etc) have desirous properties for a non-elastomeric support layer such as their ability to provide a secure chemical bond to some thermoplastic elastomer (TPE) gripping layers and their preferred ability to withstand chemical attack from some soaps and other shaving preparations. However the creep moduli of these materials is generally inferior to that of so-called engineering thermoplastics such as ABS, Polyoxymethylene (POM, commonly known as acetal) and other well known materials.
Other typical joining methods that might be considered by one of skill in the art include use of a snap fit joint. In one type of well known snap fit joint between two mating component parts, one component part is provided with an extension with a laterally extending protrusion, usually at or near the distal end portion of the extension. During assembly of the two parts the extension undergoes preferably elastic deformation as the lateral protrusion passes around a suitable shelf of the second part before snapping into a mating recess or void of the second part. As the deformation is preferably predominantly elastic, snap fit joints can be permanent or temporary, ie separable and reattachable. As the assembly of the two parts requires deformation of the extension, clearance is generally provided between the two parts to accommodate this deformation during relative motion of the two parts as these come together at assembly. One of skill in the art will understand that even if a snap fit joint is intended to be permanent it can be released if a force of appropriate magnitude and direction can be applied to the snap fit features. One of skill in the art will also understand that when a razor is accidentally dropped impact forces are generated that are generally unpredictable in magnitude, direction and transference through the razors structure and its component parts.